Movies in the 70's & 80's was it stereo or mono?

It would depend on the movie and theatre. Surround sound started in a big way around the mid 70's with Star Wars using two optical tracks (Dolby Stereo system). Some films were done in stereo prior to that using magnetic tape but this made the films expensive to produce. The Dolby Stereo optical system was the big breakthrough (two optical tracks gave four channel sound) because it was cheap to distribute.

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The reason I asked is that I'm about to rent a 1971 movie from Netflix and it states that it is in Dolby Digital Mono, whatever the heck that is.
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Right around the time Star Wars: A New Hope was released (1977), I went to see the premier of The Grateful Dead Movie at the Harvard Square Theatre. They had to bring in 4 stacks (1 in each corner), amps and a mixing console to do "four channel sound". Pink Floyd really took the lead in doing that in live concert setting. I saw them at Ivor Wynn Stadium in Hamilton, Ontario in 1975 with their full two stacks in the rear and two stacks in the front 360 degree Wish You Were Here, Dark Side of the Moon, Meddle tour.

This was an expensive undertaking, resulting in very limited releases to places that could accommodate the gear. Dolby Surround (pre-digital) on optical tracks revolutionized movie sound tracks, making it more economically feasible for theaters to convert to "four channel sound". I can still remember the opening sequence with the huge Empire cruiser passing overhead, and the sound moving from the back of the theatre to the front.

Cut and pasted from wikipedia.org

Interesting history regarding movie first!

"Not only did Fantasia establish animation as a true art form, it also introduced film audiences to multi-channel sound, which played an important part in Fantasia. After the completion of The Sorcerer's Apprentice, Stokowski enlisted the Philadelphia Orchestra, of which he was the conductor, to record the music for the six remaining segments. Walt Disney was present on the sound stage during an early session, and was very pleased with what he was hearing until he heard the playback from the recording engineers. He felt the recorded version of the music sounded tinny and undynamic, and asked his engineers to see what they could do about developing a better sound system. The engineers, led by William E. Garity, responded by creating a multi-channel sound format they called Fantasound, making Fantasia the first commercial film ever to be produced in a form of stereophonic sound. The film also marked the first use of the click track while recording the soundtrack, overdubbing of orchestral parts, and simultaneous multi-track recording.

Always wanting to try new things, Walt Disney also had plans to film Fantasia in widescreen, to have the Toccata and Fugue be filmed to be 3-D and to spray different perfumes into the theater at appropriate times during the Nutcracker Suite, but those plans were never carried out."[4]

depends on the film.

Mitch - that particular movie will play in it's original mono sound format. The movie's original mono soundtrack was encoded into Dolby Digital for use on the DVD. Dolby Digital may be scaled from mono up to 5.1 discreet channels depending on the source.

You may want to try a few of the DSP modes in your processor to get some simulated ambiance. My receiver, for example, has a DSP mode called "mono movie" which is actually a pro-logic mode that gives mono sources some extra ambience. Running it through Pro-Logic II movie mode may give you a pretty good simulated surround ambiance, but just like processing stereo music into surround, your results will vary depending on the source material. Cheers!

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ok.....thanks John
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